短路电流水平计算器
根据电源计算配电箱处的预期短路电流。
Reads AS/NZS 3008.1.2:2017 (NZ), AS/NZS 3008.1.1:2017 and 2025 (AU) and AS/NZS 3000:2018. Tables checked 27 Sept 2026.
尝试一个工程 8
每项工作都会预填示例数值。请替换为您自己的数值。
- Find the fault level at a sub‑boardThe fault current at a board 45 m from a 300 kVA transformer, against 6 kA breakers.
- Check breakers beside a 1000 kVA transformerWhether 25 kA breakers suit a main board 20 m from a 1000 kVA transformer.
- Find the fault level at a house boardThe fault current at the end of 20 m of 16 mm² mains.
- Find the fault level at a shedThe fault current 60 m down a 16 mm² submain.
- Find the fault level at an MCCThe fault current 30 m from a 500 kVA transformer.
- Check 6 kA breakers at a tenancy boardWhether 6 kA devices suit the fault level at the board.
- Find the fault level on parallel feedersThe fault current with two cables per phase.
- Find fault level from a 10 kA serviceThe fault current at a board in Australia.
输入
使用默认输入值的示例计算。
- 来源
- 变压器
- 变压器额定值
- 500 kVA
- 变压器阻抗
- 4.5 %
- 线电压
- 400 V
- 标准
- NZ · AS/NZS 3008.1.2
- 分干线长度
- 30 m
- 导体规格
- 35 mm²
- 材料
- 铜
- 绝缘
- PVC 75 °C
- 芯线
- 多芯
- 并联电缆
- 1
- 断路器分断能力
- 15 kA
配电箱处的三相故障电流
10.01kA
- 相对地故障电流，最大值
- 3.18kA
- 相对地故障电流，电缆带电
- 2.63kA
- 每相电源阻抗
- 14.4mΩ
- 分断能力
- 15kA
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 变压器每相阻抗，U² ÷ S × Z%0.01Ω
- 电源处的故障电流16.04kA
- 工作温度下分配电路相线电阻0.02Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 20 °C 时分配电路相线电阻0.02Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 分配电路相线电抗0Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 保护导体规格10mm²
AS/NZS 3000:2018 Table 5.1
- 20 °C 时的保护导体电阻0.06Ω
AS/NZS 3008.1.2:2017 Table 30 (Xc), Tables 34–35 (Rc) p.98, p.102–103
- 配电板处的三相故障电流，U0 ÷ |Z|结果10.01kA
- 配电板处的相对地最大故障电流3.18kA
- 相对地故障电流，电缆处于工作温度2.63kA
- 断路器的分断能力15kA
关于此计算器
How this is calculated
The tool finds the fault current at a board. The source is a transformer or a stated supply fault level. A submain then adds impedance. The tool compares the result with the breaking capacity of your device.
- Source impedance. For a transformer, the tool works Z = U² ÷ S × Z% per phase. It takes the source as all reactance. That gives the highest current for the size.
- Source current. It gives the fault current at the transformer terminals.
- Submain impedance. It reads the resistance and reactance of the submain for your size, length and material. The tables are Table 30 for reactance and Tables 34 and 35 for resistance. It scales the resistance to 20 °C for the maximum figure.
- Protective conductor. It reads the earth conductor size from Table 5.1 of AS/NZS 3000:2018. It adds that resistance to the earth loop.
- Fault currents. It gives the three‑phase current as U0 ÷ |Z|. It also gives the phase-earth current, maximum and with the cable hot.
- Breaking capacity. It compares the three‑phase current with the rating you enter.
| Step | Table or clause | What it decides |
|---|---|---|
| Submain reactance | AS/NZS 3008.1.2 Table 30 | The reactance of the submain |
| Submain resistance | AS/NZS 3008.1.2 Tables 34 and 35 | The resistance of the submain |
| Earth conductor | AS/NZS 3000 Table 5.1 | The size of the protective conductor |
Worked example
- 500 kVA transformer with a 30 m 35 mm² submain. The transformer has 4.5 % impedance. The three‑phase fault current at the board is 10.01 kA. The maximum phase-earth current is 3.18 kA. A 15 kA device passes.
Limits
- The tool works at nominal voltage. It does not apply the IEC 60909 voltage factors.
- It takes the network above the transformer as infinite. A real network lowers the current a little.
- It takes the phase-earth loop at the transformer as its phase impedance, as for a Dyn transformer.
- It does not add motor contribution. It does not grade devices. Use the IDMT tool for grading.
- The result is an estimate for sizing. Ask the network company for the supply fault level at the point of supply.
See also: Prospective fault current at a board, Fault level at a sub‑board on a 300 kVA transformer and Fault rating.
问题
结果仅供设计参考。请依据现行标准核对。
短路电流水平工具如何计算电流？
工具按相加上阻抗。变压器按 U² ÷ S × Z% 计算，电源按相电压除以其短路电流水平计算。分干线则依据 AS/NZS 3008.1 阻抗表加上其电阻和电抗。相电压除以总阻抗即为配电盘处的三相故障电流。
为何有两个相对地数值？
表中的电阻值为导体工作温度下的数值。冷态电缆给出的电流最大，因此最大值将电阻换算到 20 °C。热态数值较低，用于回路阻抗工具中的切断时间检查。
工具对电源作了什么假设？
它将电源视为纯电抗，并将变压器上游电网视为无限大。对于您输入的数据，两者均给出最大电流。它使用标称电压，不含 IEC 60909 电压系数。采用供电电源时，须输入进线端的 Ze 才能得出相对地数值。
结果该怎么用？
将其与配电箱断路器的分断能力进行比较。随后将其用于短路耐受计算器，以核查电缆能否在切断时间内承受该故障。
计算示例
- Starting a loaded conveyorA 22 kW conveyor that needs 120 % torque to break away. Why star-delta and a soft starter will not start it, and what a drive or autotransformer does.
- Fault level at a sub‑board, 300 kVA transformerWork the prospective fault current at a sub‑board 45 m from a 300 kVA transformer, three‑phase and phase-earth, and check 6 kA and 10 kA breakers against it.
背景
本工具读取的条款和表格
- AS/NZS 3000:2018 Table 5.1Minimum earthing conductor size by active conductor size
- AS/NZS 3008.1.2:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
- AS/NZS 3008.1.1:2017 Table 30, 34, 35Reactance at 50 Hz and a.c. resistance at 50 Hz
- AS/NZS 3008.1.1:2025 Table 4.1(A), 4.1(B), 4.5(A), 4.5(B)Reactance at 50 Hz and a.c. resistance at 50 Hz
表格最后核对于 27 Sept 2026。
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有问题，或数值看起来有误？联系我们。